PROJECT SUMMARY/ABSTRACT We propose to acquire a state-of-the-art Structured Illumination Microscope that will allow biomedical researchers at The Ohio State University and Nationwide Children's Hospital to visualize dynamic structures and temporal processes in cells and tissues that are beyond the limitations of our existing conventional microscopes. The Nikon N-SIM Structured Illumination Microscope combines significant resolution improvement in three dimensions, live cell imaging capability, and the greatest flexibility in sample preparation to provide super-resolved imaging for a wide range of users. Because there are no SIM microscopes in Ohio, the Nikon N-SIM will fill a significant technology gap. The instrument will be optimally situated in Ohio State's Campus Microscopy and Imaging Facility, a centralized shared resource that provides the central Ohio biomedical research community with 24/7 access to high-quality microscopy equipment and services. The Nikon N-SIM will directly benefit 12 major and 4 minor users with more than 20 studies funded by a broad range of NIH Institutes including NCI, NEI, NHLBI, NIAMS, NIDCD, NIBIB, NIGMS, NINR and NINDS. These researchers ? who represent 2 institutions, 5 colleges and 15 departments ? will utilize 76% of the instrument's accessible user time (AUT) to: (1) examine the spatial and temporal expression, localization, and interaction of bacterial proteins during formation of biofilms; (2) study mechanisms of cancer initiation and progression, and develop new anticancer treatments; and (3) elucidate molecular mechanisms of synapse signaling, cell division and tissue development. The balance of AUT will support several minor users and other members of the large community of biomedical researchers who routinely utilize the Campus Microscopy and Imaging Facility. The installation of this system at Ohio State will meet a clear need for super-resolution imaging particularly of live cells, be integrated into a highly collaborative and accessible environment, end costly delays for researchers who currently must seek this technology elsewhere, and lead to new discoveries in cellular/developmental biology, cancer, and infectious diseases.